1. Field of the Invention
The invention relates to a novel process for the preparation of acetoacetarylamides of the general formula: 
in which R is one or more substituents from the series alkyl, alkoxy or hydrogen.
Acetoacetarylamides are important starting materials for the preparation of colored pigments, but are also used for the preparation of agrochemical active ingredients (Ulmann""s Encyclopedia of Industrial Chemistry, 5th Edition, vol. 15, p. 71).
2. Background Art
The preparation of acetoacetarylamides has been known for some time and is based on the reaction of diketene with corresponding aromatic amines in a variety of organic and aqueous solvents and solvent mixtures (Ullmann""s Encyclopedia of Industrial Chemistry, 5th Edition, vol. 15, p. 71).
The process is usually carried out batchwise in water or aqueous solutions.
Accordingly, German Published Patent Application No. 2,519,036 discloses the preparation of various acetoacetarylamides by simultaneous metered addition of diketene and corresponding aromatic amine in the presence of water or aqueous solutions. The resulting acetoacetarylamide is cooled in the reaction mixture and left to crystallize out. Centrifugation and drying give the acetoacetarylamides in good yield and high purity.
Furthermore, European Published Patent Application No. 0648738 discloses a continuous process for the preparation of acetoacetarylamides. This involves continuously reacting diketene with the aromatic amine in a water/alcohol mixture with the reaction mixture having as long a residence time as possible in the reactor. The resulting acetoacetarylamide is isolated by crystallization of the product stream discharged from the reactor. The acetoacetarylamide prepared by the classic process satisfies all requirements in terms of quality and purity. It has, however, been found that for further processing, e.g., for pigment preparation, which usually involves the dissolution of the acetoacetarylides in aqueous alkalis, the finely crystalline powder form is more of a disadvantage. Thus, in addition to the undesired formation of dust, the slow dissolution rate in aqueous alkalis is somewhat unsatisfactory.
An object of the invention is to prepare acetoacetarylamides in a form which does not have the above-mentioned disadvantages. Moreover, an object of the invention is to provide an economic process which permits acetoacetarylamide preparation at a relatively low cost. The objects of the invention are achieved by the process of the invention and by the acetoacetarylamides in the form and with the properties according to the invention.
The acetoacetarylamides are defined by the general formula: 
in which R is hydrogen or one or more substituents from the series alkyl, alkoxy or halogen, are a solidified melt in a form which can be used in industry and is easy to handle, and have a water content between 3 and 15 percent by weight.
An alkyl group is expediently taken to mean a C1-4-alkyl group, namely, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or t-butyl. A preferred alkyl is methyl. The alkoxy group has meanings corresponding to the alkyl group. Here too, preference is given to methoxy. Halogen represents fluorine, chlorine, bromine or iodine, preferably chlorine. R is particularly preferably an arylamide radical of aniline, o-anisidine, o-toluidine, m-xylidine, o-chloroaniline, 2,4-dimethoxyaniline, 4-isopropylaniline, 4-ethoxyaniline, 2,5-dimethoxyaniline or 4-chloro-2,5-dimethoxyaniline.
The term xe2x80x9cform which can be used in industry and is easy to handlexe2x80x9d includes those application forms which can be obtained from a solidified melt using methods customary in the expert field. Nonexhausted examples include: pastilles, flakes, tablets or prills. The dimension and size of such application forms is dependent on such pastilling, flaking, tabletting or prilling processes and can vary within a wide range. The novel acetoacetarylides also have improved flowability compared with an acetoacetarylide according to the prior art.
The bulk density of the novel acetoacetarylides is expediently in the range from 0.3 to 0.8 kg/l, preferably in the range from 0.5 to 0.7 kg/l.
The specified term xe2x80x9cwater contentxe2x80x9d can also mean a content of any mixture of water with an additional solubility promoter, which can originate from the reaction, such as, aliphatic carboxylic acids such as acetic acid, ketones such as acetone or ethyl methyl ketone, C1-C4-alcohols or glycols such as ethylene glycol.
The novel acetoacetarylides have a reduced characteristic melting point compared with the dried product.
The novel acetoacetarylamides dissolve in a 0.5 N sodium hydroxide solution at 20xc2x0 C. in from approximately half to one third of the time required by a dried acetoacetarylide prepared according to the prior art.
Preferred acetoacetarylides with their characteristic properties are:
(a) acetoacetanilide, water content expediently from 5 to 15 percent by weight, preferably from 9 to 11 percent by weight; melting point expediently from 50xc2x0 to 70xc2x0 C., preferably from 57xc2x0 to 62xc2x0 C.; solubility in 500 ml of 0.5 N NaOH, 60 g pastilles having a diameter of 0.6 cm in from 10 to 20 minutes.
(b) o-Acetoacetanisidide, water content expediently from 3 to 12 percent by weight, preferably from 6 to 9 percent by weight; melting point expediently from 60xc2x0 to 80xc2x0 C., preferably from 72xc2x0 to 75xc2x0 C.; solubility in 500 ml of 0.5 N of NaOH, 60 g pastilles having a diameter of 0.6 cm in from 10 to 20 minutes.
(c) o-Acetoacetotoluidide, water content expediently from 5 to 15 percent by weight, preferably from 8 to 12 percent by weight; melting point expediently from 80xc2x0 to 100xc2x0 C., preferably from 82xc2x0 to 94xc2x0 C.; solubility in 700 ml of 0.5 N NaOH, 60 g pastilles having a diameter of 0.6 cm in from 10 to 20 minutes.
(d) m-Acetoacetoxylidide, water content expediently from 3 to 12 percent by weight, preferably from 4 to 8 percent by weight; melting point expediently from 65xc2x0 to 85xc2x0 C., preferably from 68xc2x0 to 73xc2x0 C.; solubility in 700 ml of 0.5 N NaOH, 60 g pastilles having a diameter of 0.6 cm in from 10 to 20 minutes.
(e) o-Acetoacetochloroanilide, water content expediently from 3 to 12 percent by weight, preferably from 5 to 8 percent by weight; melting point expediently from 75xc2x0 to 95xc2x0 C., preferably from 89xc2x0 to 93xc2x0 C.; solubility in 500 ml of 0.5 N NaOH, 60 g pastilles having a diameter of 0.6 cm in from 10 to 20 minutes.
The preparation of the novel acetoacetarylides initially takes place in a known manner by the reaction of diketene with the corresponding aromatic amine in the presence of water or aqueous solutions or water with a suitable solubility promoter, such as acetic acid. According to the present invention, the reaction is carried out such that the resulting acetoacetarylide is produced as a melt, the melt is removed from the reaction medium after the reaction is complete at the reaction temperature, and, after cooling, is converted into the form which can be used in industry and is easy to handle.
The preparation can either be carried out batchwise, for example, in a classic stirred apparatus, or continuously, for example, in a tubular reactor. The reaction is preferably carried out continuously in a tubular reactor.
It is particularly preferable to meter diketene and the corresponding aromatic aniline into a tubular reactor simultaneously to recirculated mother liquor such that the reaction temperature is maintained at from 50xc2x0 to 100xc2x0 C. The mother liquor expediently comprises at least 80 percent by weight of water, and is preferably exclusively water. After the reaction, in accordance with the preferred process at from 50xc2x0 to 100xc2x0 C., the aqueous mother liquor is removed and returned to the tubular reactor. The acetoacetarylide melt, which has a temperature of from 50xc2x0 to 100xc2x0 C., is then solidified by cooling and converted into the form which can be used in industry and is easy to handle. This can be carried out using, for example, drum coolers customary in the expert field, which are provided with a flaking device, with belt coolers, which are provided with a flaking device, or belt pastilling machines.